When data is transmitted through an optical network, words or frames are converted into a serial bit stream and sent through optical fiber. A receiver converts the serial bit stream back to a stream of data words or frames. For example, to send a stream of parallel 16-byte data words clocked at 83 MHz through a 10.7 gigabits-per-second (Gbps) optical network, a sender converts the 16-byte data words into a 10.7 Gbps serial bit stream, and sends the bit stream through the network. A receiver converts the bit stream back to an 83 MHz 16-byte parallel data stream.
When the serial bit stream is converted back to the parallel data stream, the converted 16-byte data words may not match the original data words. For example, a few bits from the original data word may offset each converted data word. Thus, the converted data words may need to be “re-aligned” to match the original data words. The sender may insert a pattern into the serial bit stream to assist the receiver in re-alignment of the data words. This pattern is often called a “frame alignment word (FAW)” because data to be sent over an optical network is often structured as “data frames,” each frame having several hundred or more data words, and the FAW is placed at the beginning of each frame.